Supporters of Chelsea Manning delivered an estimated 100,000 signatures to the US army liaison office in Congress on Tuesday, urging the military to drop charges against the whistleblower for possession of unapproved magazines and other material and to “stop harassing” her.

Manning, the US army soldier serving a 35-year military prison sentence for leaking official secrets, was charged with prison infractions for possession of unapproved material earlier this month. Later on Tuesday, she faces a hearing on the charges, which could reportedly result in solitary confinement.

Lawyers for Manning said they had been barred from the hearing at Fort Leavenworth, Kansas, where Manning is serving her sentence for having been the source of the vast leak of US state secrets to WikiLeaks.

“Chelsea is facing serious repercussions and punishment if these charges are upheld, yet the prison has denied her the right to legal counsel, even legal counsel at her own expense,” said Nancy Hollander, one of Chelsea’s criminal defense attorneys, in a statement. “Now we have learned the prison authorities have denied her the use of the prison library to prepare for her hearing. The whole system is rigged against her.”

At the weekend, Manning said through supporters that she had been denied access to a prison legal library in advance of Tuesday’s hearing. A Pentagon spokesman who handles the Manning case said he would check on that claim.

Officials at the US disciplinary barracks at Fort Leavenworth, where Manning is being held, referred a reporter to the Pentagon.

Last week, a list of contraband material confiscated from Manning was posted to her official Twitter account. The list includes copies of the magazines Out, the Advocate, Vanity Fair and Cosmopolitan; the Senate intelligence committee report on torture; and an expired tube of toothpaste.